BELLEVUE, Wash. (AP) — Frustrated police in Washington state said Tuesday they were working to trace the steps of a missing toddler’s mother over the past two weeks because her story about the boy’s disappearance makes little sense.

The woman, Julia Biryukova, told investigators her 2-year-old son, Sky Metalwala, vanished Sunday in Bellevue when she left him sleeping alone in her unlocked car for an hour after it ran out of gas. The 30-year-old claimed she and her 4-year-old daughter walked to a gas station, and when they returned to the car, the boy was gone.

“Given the limited amount of information we have, the fact that there’s really no solid leads to follow up on in regard to where he might be — absolutely, we suspect foul play,” Police Maj. Mike Johnson told reporters. “Nothing about the story adds up. Something else happened.”

When investigators questioned relatives, family friends and neighbors, only Biryukova and the boy’s sister reported seeing him in the past two weeks, said Bellevue police spokeswoman Carla Iafrate.

The girl told police Sunday her brother had been in the car when they left it, Iafrate said. A detective trained in questioning children interviewed her again Monday, Iafrate said, but “nothing significant” came out of it.

Detectives were working to collect surveillance video from any place Biryukova may have been over the past two weeks, Iafrate said. She has so far declined to take a polygraph examination; neither she nor her lawyer returned calls or emails seeking comment Monday and Tuesday.

Sky’s disappearance came amid a bitter divorce and custody fight between Biryukova and the boy’s father, Solomon Metalwala. At a mandatory mediation session last week, the parties reached a tentative agreement that would allow Metalwala to have some visitation with Sky and his older sister, said Metalwala’s lawyer, Leslie Clay Terry III.

Investigators have invited the boy’s relatives to take polygraph tests in hopes of shaking loose any clues to his whereabouts. Metalwala took one Monday night but it was inconclusive; he offered to take another one Tuesday, but Iafrate did not immediately know whether the second test took place.

Biryukova claimed she had been driving to a Bellevue hospital because Sky wasn’t feeling well when the car ran out of gas, police said. The hospital wasn’t the closest one to her home in nearby Redmond, but she reportedly told detectives she liked the Bellevue hospital better. It wasn’t immediately clear what might have been wrong with the boy.

If Sky was in fact left in the car, it wouldn’t have been the first time.

When he was 3 months old, his parents left him in their SUV in a Target parking lot for 55 minutes on a 27-degree day, court records showed. The couple came out of the store to get Sky only after police arrived and asked for the vehicle’s owner to be paged.

Redmond police cited both parents for reckless endangerment in the December 2009 incident. However, the case was dismissed early this year after the pair completed a year of probation, 40 hours of community service and a 10-week parenting class.

In court documents filed in their divorce, Biryukova said their relationship deteriorated in 2008 after they bought an expensive home in Kirkland and couldn’t keep up with the payments on that property and a condominium they owned.

The divorce case has been marked by back-and-forth protection orders. She accused her husband of beating her and the children; he alleged she had severe psychiatric problems that endangered them.

Terry said state Child Protective Services later conducted an investigation that cleared Metalwala.

Meanwhile, a social worker reported this year that a doctor found Biryukova to be in good mental health and an appropriate caregiver for the kids.